1. Technical Field
This invention relates generally to pistons for internal combustion engines, and more particularly to pistons having wrist pin lubrication features.
2. Related Art
Piston constructions having one or two (dual gallery) generally closed oil cooling galleries are known. Dual gallery pistons have an annular, radially outer gallery and a central gallery formed between upper and lower crown portions, wherein the central gallery is typically formed as an open gallery beneath the combustion bowl wall. The outer and central galleries can be isolated from one another or in fluid communication with one another via oil passages. In addition, it is known to provide pin lubrication passages extending from one or both of the galleries to a wrist pin. The lubrication passages can extend into a wrist pin bore of a pin boss and/or through an opening in a lower inner gallery floor between laterally spaced pin bosses. The outer gallery is particularly effective in cooling an outer ring belt region of the piston, while the central gallery is particularly effective in cooling a central crown region, formed in part by an upper combustion wall, which is directly exposed to hot combustion gases. Although these gallery constructions are generally effective in cooling the piston, the oil flow dynamics through the galleries can be improved, with particular regard to the central gallery, thereby enhancing the ability to cool pistons in use.